The present invention relates to the synchronization of dynamic angular and time domain control systems, and in particular, to a hardware-based system for performing angle-to-time and time-to-angle conversions in a dynamic angular measurement and control system.
When measuring the angular position of a rotating object via a periodic input that represents a rotation of a fixed number of degrees, it is often desirable to increase the resolution of the system by interpolating between inputs. If the angular velocity of the object is changing dynamically, the relationship between angle and time also changes, and the interpolation algorithm must be performed for each new input that is received.
In the example of automotive powertrain control systems, there is a relationship between the angle of the crank shaft and the time between angles as the crankshaft rotates. The normal operation of a 4-cycle engine repeats itself every two revolutions of the crankshaft, or every 720xcex8. Various events (e.g., opening or closing valves, generating sparks, injecting fuel, etc.) are desired to be triggered at time offset from a certain angular position. For example, it may be desired to trigger an event 10 ms (milliseconds) prior to an angle of 60xcex8. The control system then has to make a determination as to when 10 ms prior to 60xcex8 occurs.
Typical prior art control systems rely upon the execution of software algorithms to perform these conversions. There are various problems with prior art control systems. For example, the software algorithms require significant CPU (central processing unit) computing and interrupt processing bandwidth. In addition there are delays in making the required determinations caused by CPU loading of other tasks and interrupt latency. Another problem is that the accuracy is limited in prior art systems.